+0.45%Safe swap — speedometer error is minor
Speedometer error
With a speedometer calibrated to 245/55R19, fitting 275/45R20 makes it read as follows:
| Speedo shows | True speed | Speedo shows | True speed |
|---|---|---|---|
| 40 km/h | 40.2 km/h | 25 mph | 25 mph |
| 60 km/h | 60.3 km/h | 37 mph | 37 mph |
| 80 km/h | 80.4 km/h | 50 mph | 50 mph |
| 100 km/h | 100.5 km/h | 62 mph | 62 mph |
| 120 km/h | 120.5 km/h | 75 mph | 75 mph |
Full comparison
245/55R19
Overall diameter752.1 mm · 29.61 in
Section width245 mm · 9.65 in
Sidewall height134.8 mm · 5.31 in
Circumference2362.8 mm · 93.0 in
Revolutions per mile681
Revolutions per km423
275/45R20
Overall diameter755.5 mm · 29.74 in
Section width275 mm · 10.83 in
Sidewall height123.8 mm · 4.87 in
Circumference2373.5 mm · 93.4 in
Revolutions per mile678
Revolutions per km421
+0.45%Safe swap — speedometer error is minor
Original
Overall diameter752.1 mm · 29.61 in
Sidewall height134.8 mm
Circumference2,362.8 mm
Revolutions / mile681.1
New
Overall diameter755.5 mm · 29.74 in
Sidewall height123.8 mm
Circumference2,373.5 mm
Revolutions / mile678.1
Speedometer & odometer error
The new tire changes overall diameter by +0.45%. With a speedometer calibrated to the original tire, that same percentage is how far the speedometer and odometer read off — a taller tire means your true speed is higher than indicated and the odometer under-counts distance.
| Speedo shows | True speed | Speedo shows | True speed |
|---|---|---|---|
| 40 km/h | 40.2 km/h | 25 mph | 25 mph |
| 60 km/h | 60.3 km/h | 37 mph | 37 mph |
| 80 km/h | 80.4 km/h | 50 mph | 50 mph |
| 100 km/h | 100.5 km/h | 62 mph | 62 mph |
| 120 km/h | 120.5 km/h | 75 mph | 75 mph |
See individual specs: 245/55R19 · 275/45R20. A change this size can affect ABS/speed calibration — see wheel-speed codes if a light appears.